Tilting mechanism

ABSTRACT

A tilting conveyor cart for a sorting conveyor for transporting objects and unloading objects at one or more unloading stations adjacent the conveyor. Each of the tilting conveyor carts includes a trailer frame base, a carrying tray for holding the objects and a tiltable support apparatus for supporting the carrying tray above the trailer frame base and for allowing tilting of the carrying tray towards at least one side of the conveyor to unload objects into unloading stations on at least one side of the conveyor.

This application is a division of utility application Ser. No.09/518,698 filed Mar. 3, 2000 and now U.S. Pat. No. 6,382,392.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates generally to package sorting conveyors andmore particularly relates to an improved tilting mechanism for a tiltingconveyor cart.

(2) Description of the Related Art

Conveyor systems having a number of individual carrying carts have beencommonly used for many years to carry and sort packages or other items,such as mail. For example, U.S. Pat. No. 5,054,601 to Sjogren et al.discloses a package sorting conveyor comprised of a train of tilt traycarriers coupled in tandem to form a continuous loop. Each carrierincludes a pivotally mounted tilt tray normally maintained in an uprightposition. The carriers are moved around the loop by a series of motorsspaced around the loop. Branching out from the loop are outfeed chutesor the like for receiving packages from the carriers. When a particularcarrier holding a particular package to be sorted reaches a selectedoutfeed chute, an actuator tilts the tray to dump the package into theoutfeed chute. Another example of a typical package sorting conveyor isdisclosed in International PCT Application Number PCT/DK90/00047 ofKosan Crisplant A/S.

One significant disadvantage of conventionally designed package sortingconveyors is that conventional conveyor carriers laterally tilt only ona horizontal axis parallel to the direction of conveyor travel. Whilethis accomplishes the objective of dumping the package from the carrierinto an outfeed chute or the like, the package is often roughly tumbledor rolled, sometimes damaging the package's contents. One reason forthis is that the packages typically are unloaded from the carrier whilestill traveling forward at the same speed as the conveyor. Thus,packages tend to slam into a forward retaining wall of the outfeed chutebefore sliding down the chute. Another problem with conventionallaterally tilting conveyors is that because the packages are movingforward at full speed when they are unloaded into the outfeed chute, theoutfeed chute must be relatively wide so that packages do not miss thechute and fall off the conveyor past the chute. This often unnecessarilyincreases the overall size of the conveyor system.

U.S. Pat. No. 4,744,454 and an improvement thereto, U.S. Pat. No.5,086,905, both to Pölling, disclose previous attempts to remedy thisproblem of rough handling by conventional laterally tilting conveyorcarriers. Both of these patents to Pölling disclose a conveyor elementfor a package conveyor that includes a tilting carrier tray mounted tobe rotatable about two swivel axes. A first swivel shaft extendsobliquely downward from the underside of the carrying tray and is inturn connected at an angle to the end of a second swivel shaft extendingobliquely upwards from a base support part of the conveyor element.Together, the two swivel shafts form a “V” that points in the directionof conveyor travel. Both of the swivel shafts lie in the vertical planeof symmetry of the conveyor element when the carrier tray is disposed inits upright position.

Because the carrier tray of Pölling rotates about two oblique axes, thecarrier tray can be tilted not only lateral on a horizontal axis, but ismoved through a geometrically complex spatial reorientation duringpackage discharge. This allows for more gentle placement of a package onan outfeed chute than can be accomplished using conventional conveyortrays that laterally tip on only a horizontal axis. The Pölling conveyorelement more gently handles the packages by imparting some degree ofrearward velocity to the packages as they are discharged, which, whenadded to the forward velocity of the conveyor system, results in thepackages' forward velocity during discharge being less than that of theconveyor system itself.

However, the conveyor elements of both of Pölling's patents are undulycomplicated and intolerant of manufacturing discrepancies. In fact, thesecond Pölling conveyor element (U.S. Pat. No. 5,086,905) was inventedin an attempt to simplify the original design disclosed in the firstPölling patent (U.S. Pat. No. 4,744,454), which had proved to be tooexpensive and complicated to manufacture efficiently. As a result ofthis complexity and cost, the Pölling devices have not enjoyedsignificant commercial acceptance and success.

One solution to these problems is shown in U.S. Pat. No. 5,836,436,issued Nov. 17, 1998 and co-owned by the assignee of the presentinvention, which is hereby incorporated by reference in its entirety.One feature of this reference is the use of a pull-down design fortilting the improve trays.

Another example of a sorter conveyor using a pull-down design fortilting its trays is shown in U.S. Pat. No. 5,664,660, issued to Prydtz.The '660 patent is directed to a sorter conveyor having laterallytiltable transport trays, instead of a conventional transport chaindriven by a driving station, in which a driving wheel or worm cooperateswith the chain links, these being advanced arranged with guiding railsalong a small mutual spacing and carrying both the transport trays andthe tilt mechanisms associated therewith, which conventional arrangementcauses considerable problems with respect to tolerances for both thelongitudinal pitch of the chain links and the mounting of the guidingrails. The invention includes carts that are advanced along mutuallywidely spaced guiding rails, whereby the tolerance demands on the latterare reduced considerably. Also, the carts are advanced by way ofstationary linear motors, which, supposedly, renders any tolerancedemands on the longitudinal pitch of the tray units entirelysuperfluous. Also the tilting mechanisms may be given a very simpledesign according to the patent. However, it has been discovered thatthere are operational problems associated with this type of design,especially the operation of its linear motors and tilting mechanism.

While the design shown in U.S. Pat. No. 5,836,436 overcomes some of theproblems associated with the prior art designs, some problems have begunto surface over time as the units have been operated. One of theseproblems is when there is a mis-tip which causes “cascading errors.”

“Cascading errors” were first discovered when audits at the end of thechute indicated there were more errors occurring than were predicted byerrors indicating by tray verification. Normally, when a tray is to tipto the right immediately before the tray is being straightened, a seriesof photocells determines if the right hand arm is in the “low” or“tipped” position, or the “up” or “latched” position. If the controlssaid that the arm should be tipped and the verifier says that the arm istipped then it was assumed that the product went down the correct chute.However, in certain cases, tray verification would predict five errorsbut chute audits would indicate 35 errors. This previously unknowneffect is referred to in this application as “cascade errors.”

Most pull-down tilting mechanisms are actuated by spring when the pivotswitch is released by an energizing solenoid. In other words, the pivotswitch is spring-biased in the “out” position but held in the retainedposition by the solenoid.

When the computer provides a pulse, the solenoid plunger retracts,enabling the pivot switch to spring into the “out” position. The wheelstrikes the pivot switch in front of the pivot point and the pivotswitch unlatches the carriage and then as the wheel strikes the tail ofthe pivot switch, it pushes the pivot switch back to the home positionand the spring on the solenoid plunger pushes the plunger into a detentcapturing the pivot switch in the home position. The computer initiatesthe unlatch but it is the action of the wheel on the tail that normallyrelatches it.

If the solenoid does not return to capture the pivot switch before thewheel leaves the pivot switch's tail or a wheel is missing or broken,this will allow the pivot switch to move away from its intended homeposition back into the engagement position. The next tilt module that isnot in the down position will then strike the pivot switch, tilt, andreset the pivot switch. If the pivot switch relatches properly thistime, then that particular pivot switch will cause no more errors. Ifthe pivot switch does not relatch it can again go into the engagedposition and cause additional problems.

The cascade effect, though, comes from the first carriage that wastipped incorrectly, for if it were assigned a tilt position furtherdownstream, when that carriage (which has been tilted incorrectly) getsin position to unload, the pivot switch at the proper destination chutewill move into the engagement position. But because that arm has beenincorrectly tipped upstream, no action will take place and the pivotswitch will stay in the out position until the next untipped carriagearrives. That carriage will then be tipped at the wrong destination butshould cause that pivot switch to relatch. If that particular tray wasassigned a chute destination further downstream, when it arrives at itsproper destination, the pivot switch will move into the engagementposition, but again cannot engage because the tilt module is already inthe low position, the tilt module will pass by and will not relatch thepivot switch. This pivot switch will then stay in the out positioncapturing the wheel of the next tilt module that is not tipped. Thiserror will than continue to cascade downstream until eventually theerror will pass the last destination and the system should heal itself.

However, there are some conditions that can exist that cause the errornot to heal itself but continue to cause problems. An example would beif a particular tilt module were missing a wheel; that tilt module couldthen be loaded and when it gets to its destination, the pivot switchwill go out to engage the wheel but with no wheel the module will nottip. The pivot switch will then catch the next available tray beginningthe cascade problem. This will continue to repeat itself and will occurand start cascade error any time the tray with the missing wheel isassigned a destination.

One attempted solution to this problem is to use the tip verificationswitch to shut the sorter down if the pivot switch does not return tothe “home” position within a given time period. However, with a largesorter this requires a maintenance man to then check the pivot switch tosee if it should be reset and whether a wheel is missing. In themeantime, everything just sits on the sorter. For time criticalapplications, such as airline baggage sorting, this delay may beunacceptable.

One solution to these problems is shown in U.S. Pat. No. 6,009,992,issued Jan. 4, 2000 and also owned by the assignee of the presentinvention, which is hereby incorporated by reference in its entirety.One feature of this reference is the use of a powered up and powereddown bidirectional pivot switch.

However, most of these designs are based around linear induction motors(LIMs) which are well accepted today due to their quietness and lowmaintenance. Unfortunately, for all their advantages LIMs are not veryenergy efficient. For example, pairs of LIMs, spaced at 80 feetintervals and operated at 480 volts, draws about 15 amps. This is about90 watts per foot of sorter for about 70 pounds of thrust. To thecontrary, prior art chain drives would draw about 15 watts per foot ofsorter for about 1500 pounds of thrust. Thus, the modern LIM drives, forall their other advantages, are energy hogs. However, prior art,mechanical chain drives are just too noisy and high maintenance fortoday's market.

One solution to these problems is shown in U.S. application Ser. No.09/504,052, filed Feb. 14, 2000 and also owned by the assignee of thepresent invention, which is hereby incorporated by reference in itsentirety. One feature of this reference is the use of a mechanicalroller motor design to assist or replace the LIM drives.

Finally, another problem which has recently become apparent is whenlarger loads are tipped on a pulldown-type sorter, the larger loadtransfers its momentum to the end of the actuating arm, causing the endto the arm to “slap” into the side of the descending ramp wall. As canbe appreciated, since a major factor in the decision to buy a LIM driveis the quietness of the drive, a significant increase in operating noisewhen heavy loads are tipped is not desirable.

Thus, there remains a need for a new and improved tilting mechanism fortilting a conveyor tray that reduces the sound of a tip while, at thesame time, is an uncomplicated design that is inexpensive and simple tomanufacture and service.

SUMMARY OF THE INVENTION

The present invention is directed to an improved tilting mechanism for aconveyor cart for a sorting conveyor for transporting objects andunloading objects at one or more unloading stations adjacent theconveyor. Generally, the sorting conveyor includes: a conveyor track; atrain of the tilting conveyor carts connected end-to-end; and a powersource for moving the conveyor carts on the conveyor track. In thepreferred embodiment, the power source is a linear induction motor.

Each of the tilting conveyor carts includes a trailer frame base. Thetrailer frame includes a roller structure for engaging the conveyortrack, a driven member responsive to the power source, and a hitchmechanism for connecting each tilting conveyor cart to an adjacentconveyor cart. The conveyor cart also includes a carrying tray forholding the objects and a tiltable support apparatus for supporting thecarrying tray above the trailer frame base and for allowing tilting ofthe carrying tray towards at least one side of the conveyor to unloadobjects into unloading stations on at least one side of the conveyor.

The tilting mechanism tilts the carrying tray on the tiltable supportapparatus to thereby unload objects into one of the unloading stationsadjacent the conveyor. The improved tilting mechanism includes a pair ofactuating arms attached to the carrying tray on opposite sides of thetiltable support apparatus and a pull-down mechanism associated witheach unloading station for selectively pulling down one of the actuatingarms so as to pull one side of the carrying tray downwardly into atilted position.

In the present invention, each of the actuator arms includes a camfollower on a lower end of the actuator arm, and wherein the pull-downmechanism includes a descending ramp adjacent the conveyor track, alaterally pivoting switch for directing the cam follower of a selectedactuator arm into the descending ramp and a transverse guide forcontrolling the position of the actuator arm to reduce noise duringtipping.

In the preferred embodiment, the rotary actuator assembly includes anactuator arm having a first end and a second end, the pivot switch beingconnected to the first end of the actuator arm; and a bi-directionalactuator attached to the actuator arm second end, whereby the rotaryactuator assembly is operable to rotate the laterally pivoting switch toengage the cam follower and direct the cam follower of a selectedactuator arm into the descending ramp and for closing the laterallypivoting switch after capture of the cam follower.

Accordingly, one aspect of the present invention is to provide a sortingconveyor for transporting objects and unloading objects at one or moreunloading stations adjacent the conveyor. The sorting conveyor includes:(a) a conveyor track; (b) a train of tilting conveyor carts connectedend-to-end; (c) a power source for moving the conveyor carts on theconveyor track; (d) each of the tilting conveyor carts comprising: (i) atrailer frame base, including: a roller structure for engaging theconveyor track, a driven member responsive to the power source, and ahitch mechanism for connecting each tilting conveyor cart to an adjacentconveyor cart; (ii) a carrying tray for holding the objects; and (iii) atiltable support apparatus for supporting the carrying tray above thetrailer frame base and for allowing tilting of the carrying tray towardsat least one side of the conveyor to unload objects into unloadingstations on at least one side of the conveyor; and (e) a tiltingmechanism for tilting the carrying tray on the tiltable supportapparatus to thereby unload objects into one of the unloading stationsadjacent the conveyor, wherein the tilting mechanism includes: (i) apair of actuating arms attached to the carrying tray on opposite sidesof the tiltable support apparatus; and (ii) a pull-down mechanismassociated with each unloading station for selectively pulling down oneof the actuating arms so as to pull one side of the carrying traydownwardly into a tilted position; wherein each of the actuator armsincludes a cam follower on a lower end of the actuator arm, and whereinthe pull-down mechanism includes a descending ramp adjacent the conveyortrack, a laterally pivoting switch for directing the cam follower of aselected actuator arm into the descending ramp and a transverse guidefor controlling the position of the actuator arm to reduce noise duringtipping.

Another aspect of the present invention is to provide tilting mechanismfor a tilting cart for a sorting conveyor, the tilting cart including acarrying tray, a tiltable support apparatus and a tilting mechanism fortilting the tiltable support apparatus on the tilting cart to therebyunload objects into one of the unloading stations adjacent the conveyor,wherein the tilting mechanism includes: (i) a pair of actuating armsattached to the carrying tray on opposite sides of the tiltable supportapparatus; and (ii) a pull-down mechanism associated with each unloadingstation for selectively pulling down one of the actuating arms so as topull one side of the carrying tray downwardly into a tilted position,wherein each of the actuator arms includes a cam follower on a lower endof the actuator arm and wherein the pull-down mechanism includes: adescending ramp adjacent the conveyor track; a laterally pivoting switchfor directing the cam follower of a selected cart actuator arm into thedescending ramp; and a transverse guide for controlling the position ofthe actuator arm to reduce noise during tipping.

Still another aspect of the present invention is to provide a sortingconveyor for transporting objects and unloading objects at one or moreunloading stations adjacent the conveyor. The sorting conveyor includes:(a) a conveyor track; (b) a train of tilting conveyor carts connectedend-to-end; (c) a power source for moving the conveyor carts on theconveyor track, the power source comprises a linear induction motor; (d)each of the tilting conveyor carts comprising: (i) a trailer frame base,including: a roller structure for engaging the conveyor track, a drivenmember responsive to the power source, and a hitch mechanism forconnecting each tilting conveyor cart to an adjacent conveyor cart; (ii)a carrying tray for holding the objects; and (iii) a tiltable supportapparatus for supporting the carrying tray above the trailer frame baseand for allowing tilting of the carrying tray towards at least one sideof the conveyor to unload objects into unloading stations on at leastone side of the conveyor, the tiltable support apparatus including: (i)an upper support structure joined to the carrying tray, (ii) a lowersupport structure joined to the trailer frame base, and (iii) a pivotstructure connecting the upper support structure to the lower supportstructure along a pivot axis; and (e) a tilting mechanism for tiltingthe carrying tray on the tiltable support apparatus to thereby unloadobjects into one of the unloading stations adjacent the conveyor,wherein the tilting mechanism includes: (i) a pair of actuating armsattached to the carrying tray on opposite sides of the tiltable supportapparatus; and (ii) a pull-down mechanism associated with each unloadingstation for selectively pulling down one of the actuating arms so as topull one side of the carrying tray downwardly into a tilted position;wherein each of the actuator arms includes a cam follower on a lower endof the actuator arm, and wherein the pull-down mechanism includes adescending ramp adjacent the conveyor track, a laterally pivoting switchfor directing the cam follower of a selected actuator arm into thedescending ramp and a transverse guide for controlling the position ofthe actuator arm to reduce noise during tipping.

These and other aspects of the present invention will become apparent tothose skilled in the art after a reading of the following description ofthe preferred embodiment when considered with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of a package sorting conveyorconstructed according to the present invention;

FIG. 2 is front, elevational view of a single tilting conveyor cart ofthe package sorting conveyor and the power source of the conveyor;

FIG. 3 depicts a train of trailer frame structures of the conveyorcarts, as seen from the top, but with the tiltable support apparatusesand the carrying trays of the conveyor carts removed for clarity;

FIG. 3A depicts a top view of an axle caster that holds a cam followeron one of the conveyor carts;

FIG. 3B is a cross-sectional view of the axle caster and cam follower ofFIG. 3A, taken along lines 3B—3B;

FIG. 4 is an elevational side view of one of the tilting conveyor cartsof the present invention;

FIG. 5 is a sectional side view of a tilting conveyor cart, taken alonglines 5—5 of FIG. 2, which shows the tiltable support apparatus and theangled pivot structure of the tilting conveyor cart of the invention;

FIG. 5A is a geometric depiction of the conveyor cart pivot axis andconveyor line of travel as they relate to three-dimensional X,Y,Zspatial coordinates;

FIG. 6 is a top view of the train of carts of the package sortingconveyor of the present invention;

FIG. 6A shows the train of carts of FIG. 6, but with one of the carts inits tilted position and unloading a package onto an unloading stationbeside the sorting conveyor track;

FIG. 7 is a rear view of the tilting conveyor cart taken along lines 7—7of FIG. 4 with the track rails and the roller structure omitted forclarity, which shows the conveyor cart in its upright, horizontalposition;

FIG. 7A shows the tilting conveyor cart of FIG. 7 in its tiltedposition;

FIG. 8 is a side elevational view of the pull-down mechanism of theinvention with its switch in an open position as it captures a passingcam follower on a conveyor cart actuating arm;

FIG. 8A is another side view of the pull-down mechanism, except with thecam follower traveling through the descending ramp and the switch in itsclosed position;

FIG. 9 is a top view of the pull-down mechanism with the switch in itsopen position, capturing a passing cam follower;

FIG. 9A is another top view of the pull-down mechanism, except with thecam follower traveling through the descending ramp and the switch in itsclosed position;

FIG. 10 is a top view of the push-up mechanism;

FIG. 10A is a side view of the push-up mechanism;

FIG. 11 is a cross sectional view showing the bi-directional actuatorconnected to the pivot switch;

FIG. 12 is a cross sectional view of the actuator arm shown in FIG. 7,taken along lines 12—12; and

FIG. 13 is a cross sectional view of the actuator arm shown in FIG. 7,taken along lines 13—13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, like reference characters designate likeor corresponding parts throughout the several views. Also in thefollowing description, it is to be understood that such terms as“forward”, “rearward”, “left”, “right”, “upwardly”, “downwardly”, andthe like are words of convenience and are not to be construed aslimiting terms.

Referring now to the drawings in general and FIG. 1 in particular, itwill be understood that the illustrations are for the purpose ofdescribing a preferred embodiment of the invention and are not intendedto limit the invention thereto. As seen in FIG. 1, a sorting conveyor,generally designated 10, is shown constructed according to the presentinvention for transporting and sorting packages 11 or other objects. Thesorting conveyor 10 comprises a train of individual carts 20, connectedend to end, which preferably form an endless loop around aclosed-circuit conveyor track 12. Alternately, the conveyor carts 20 ofthe invention could be used singly or as part of a finite train.

The package sorting conveyor 10 generally includes four majorsub-assemblies: a conveyor track 12; a power source 70; the train oftilting conveyor carts 20, which are moved along the conveyor track 12by the power source 70; and a tilting mechanism 80 for tilting theconveyor carts 20 to discharge packages 11 therefrom. Typically, anynumber of unloading stations or outfeed chutes 18, which are adjacentthe package sorting conveyor 10 on one or both sides thereof, receivethe packages 11 discharged from the sorting conveyor 10 and carry thepackages to waiting storage bins, trucks, etc. Packages may be manuallyplaced on the conveyor carts 20 or may be delivered to the sortingconveyor 10 via infeed chutes 17 or the like.

The conveyor track 12 includes two parallel rails 14 and may be built toconform to the layout of any warehouse, shipping center, distributioncenter, or the like. Best seen as resembling the track of a rollercoaster, the conveyor track 12 may be substantially horizontal or mayascend and descend. The conveyor track rails 14 may lie in the samehorizontal plane, or one may be higher than the other, such as would bethe case in a banked curve in the track 12. Banked curves are greatlyadvantageous because they allow the conveyor carts 20 to move around acurved conveyor track 12 at a much greater speed without spillingpackages 11 than on a flat track. Preferably, the rails 14 are generallytubular, again similar to a roller coaster, and are supported by railsupport members 16 only on the outwardly facing edges of the rails. Therails 14 may be round or rectangular in cross-section. Rectangularcross-section is preferred since it has been found that round railscause the cam followers to wear somewhat in their center because theload is not as well distributed as when rectangular rails are utilized.

The power source 70 of the sorter conveyor 10, which is shown in FIG. 2,is preferably a vertically oriented linear induction motor (LIM). Thevertically oriented LIM 70 of the present invention is an improvementover previously designed LIM's, which typically are horizontallydisposed below the conveyor track. Conventional LIM's also usuallydepend on the presence of a heavy steel plate in each conveyor cart toprovide a pathway through which electromagnetic flux from theelectromagnetic coil of the LIM passes, thereby driving the carts alongthe track. This causes two problems. The first problem is with excessiveweight of the conveyor cart train resulting from the presence of thesteel plates.

The second problem is with maintaining the proper and constant distancebetween the electromagnetic coil of the LIM and the conveyor cart,because gravity coupled with magnetic attraction constantly try to pullthe conveyor cart downwardly towards the electromagnetic coil. Magneticattraction, which attracts the cart towards the electromagnetic coil,accounts for approximately ten percent of the force generated by theelectromagnetic coil. Longitudinal thrust, which drives the conveyorcart train around the conveyor track, accounts for approximately ninetypercent of the force generated by the electromagnetic coil. While theten percent magnetic attractive force is relatively weak compared to theninety percent longitudinal thrust force, it is still enough to pull theconveyor cart into contact with the electromagnetic coil, especiallywhen assisted by gravity in a configuration where the LIM ishorizontally disposed below the conveyor track. If the conveyor cart isdrawn into contact with the electromagnetic coil, the carts are frozenin place because even the ninety percent longitudinal thrust componentof the LIM's total force cannot overcome the friction created by thecontacting surfaces magnetically held together. This contact andresulting conveyor failure is normally prevented by maintaining adistance between the conveyor cart and the electromagnetic coil withwhatever apparatus is used to support the train of conveyor cartsmoveably on the conveyor track. However, as parts such as wheels wear,the distance between the conveyor carts and the electromagnetic coil isreduced until contact and resulting conveyor cart seizure is likely tooccur.

The LIM 70 of the present invention solves both of these problems in twodifferent ways. First, the conventional steel flux plate is replacedwith a second electromagnetic coil 72 b, which is preferably identicalto, but out-of-phase with, a first electromagnetic coil 72 a. Eachelectromagnetic coil thus performs the function of the steel plate forthe other electromagnetic coil, i.e. electromagnetic coil 72 a providesa flux path for electromagnetic coil 72 b and vice versa. Elimination ofthe conventional steel plate reduces the weight of and, accordingly, theenergy required to move the train of conveyor carts 20.

Second, the LIM 70 is vertically oriented so that a driven fin 36, whichis attached to the bottom of each conveyor cart 20, hangs between thetwo electromagnets 72 a,b. Composed of aluminum or other conductivemetal, the vertical fin 36 preferably has swept-back front 36 a and rear36 b edges, as shown in FIG. 4, giving the fin 36 a generallyparallelogram shape to reduce damage in the event the fin would contacta structure and to distribute the air gap over the length of the LIM toreduce heat and maintain more constant thrust. Vertically orienting thefin 36 and the LIM 70 greatly reduces problems with maintaining properspacing between the fin 36 and the electromagnets 72 a,b, becausegravity ceases to be a factor as the weight of the live load varies andbecause the two electromagnets 72 a,b, of the LIM 70 both attract thefin 36 equally. This results in the fin 36 being easily maintainedequidistant between the two electromagnets 72 a,b of the LIM 70 of theinvention, thereby preventing the fin 36 from contacting one of theelectromagnets and being seized in place as described above.

The electromagnets 72 a,b are out-of-phase with respect to each other sothat the inductive force they create will flow in the same direction. Inother words, the electromagnets 72 a,b are electrically out-of-phasewhile physically opposed to each other so as to supplement each other'sinductive forces on the fin 36, instead of canceling each other out.This helps provide a consistent motive force on the train of conveyorcarts because longitudinal thrust remains substantially constant even ifthe fin 36 is pulled slightly closer to one of the electromagnets 72 a,bof the LIM 70. While the longitudinal thrust is thereby increased withrespect to the closer electromagnet, the longitudinal thrust withrespect to the more distant electromagnet is proportionally decreased.Thus, total longitudinal thrust in the direction or line of travelremains constant even if the fin 36 wavers slightly from side to side.While a small degree of lateral fin movement may occur, the structure ofthe carts and the opposing pull of the electromagnets 72 a,b prevent anychange in the total thrust if the fin is pulled into close proximitywith either electromagnet. The LIM 70 ordinarily moves the train ofconveyor carts 20 in one direction of travel; however, it can also bereversed if necessary to run the sorting conveyor backwards.

Now turning to the train of tilting conveyor carts 20, each cart 20includes three major sub-assemblies, shown best in FIG. 2: a trailerframe structure 22, a generally horizontally disposed carrying tray 40for holding the packages 11, and a tiltable support apparatus 50 forsupporting the carrying tray 40 above the trailer frame structure 22 andfor allowing tilting of the carrying tray 40 towards either side of thesorting conveyor 10 to unload a package into one of the unloadingstations. Each cart 20 is built around a base trailer frame structure 22to which other components of each cart 20 are mounted. As shown in FIG.3, the trailer frame structure 22 includes a longitudinal base member 24that extends in the rearward direction of conveyor travel 64 between thetwo parallel rails 14. Preferably, the base member 24 is substantiallyequidistant from each rail 14.

A roller structure 26 for riding on the conveyor track 12 is-mounted ona front end of the base member 24 and includes two laterally extendingcam follower mechanisms 27, one for each rail 14. The reason for theoutboard placement of the rail supports 16 and the tubular shape of therails 14 becomes apparent upon examining the cam follower mechanisms 27.Each cam follower mechanism 27 includes three cam followers: an uppercam follower 30 a for riding on the top edge of the rail 14, a middlecam follower 30 b for riding on an inside edge of the rail 14, and alower cam follower 30 c for riding on the bottom edge of the rail 14.With this configuration, it is almost impossible for a cart 20 to jumpthe track 12, because a wheel is provided for each directional force(sideways, upward, and downward) that a cart 20 may encounter whentraveling along the track 12. Preferably, each cam follower 30 a,b,c isconstructed of a somewhat resilient material such as polyurethane toprovide for smooth, quiet, relatively vibration-free operation of thesorter conveyor 10.

Referring now especially to FIGS. 3A and 3B, the structure of each camfollower mechanism 27 that holds the top wheel 30 a is shown in greaterdetail. Each top cam follower 30 a is retained by an axle caster 28 thatis preferably formed from extruded aluminum or the like. The axle caster28 includes two forks 28 a and 28 b, one on each side of the wheel 30 a,and a bearing bore 28 c disposed at the juncture of the two forks 28a,b, which has an opening 28 d on one side so that the bearing bore 28 ccommunicates with the space between the forks 28 a,b. A pair of flangebearings 29 seated in the bearing bore 28 c are disposed around an axleshaft 27 a extending from the roller structure 26. Preferably formed of“oilite” or other friction-reducing material, each flange bearing 29 hasthe form of a top-hat bushing and includes a center hole 29 a throughwhich passes the axle shaft 27 a. The cam follower 30 a is held in placebetween the two forks 28 a,b by a bolt 31 and nut 31 a. Preferably, thecam follower 30 a includes a bearing structure 30 d disposed around thebolt 31, which serves as an axle running through the center of the wheel30 a.

The axle caster shown in FIGS. 3A and 3B represents an improvement overexisting axle casters that hold cam followers. Due to wear, axle castersinevitably tend to become loose and allow the cam followers to chatterback and forth, which would inhibit smooth, quiet, vibration-freeoperation of a sorting conveyor. However, previously designed axlecasters typically have a bearing around the axle shaft that must bepressed out when worn and replaced with a new bearing that must bepressed in. This requires a press in addition to more time and expensethan is desirable in a large sorting conveyor system.

The axle caster 28 of the present invention solves this problem byproviding that the flange bearings 29 can easily be slid into place byhand into the bearing bore 28 c without using a press. Then, toimmovably secure the flange bearings 29 inside the bearing bore 28 c,the forks 28 a,b are slightly flexed inwardly towards each other as thenut 31 a is tightened onto the bolt 31 to hold the wheel 30 a in place.The forks 28 a,b of the axle caster 28 are therefore formed minutelywider apart than would be necessary to merely hold the wheel 30 a. Whenthe forks 28 a,b are flexed inwardly towards each other by tighteningthe nut 31 a on the bolt 31, the opening 28 d of the bearing bore 28 cis closed somewhat and the bearing bore 28 c is itself slightlydistorted, securely retaining the flange bearings 29 therein. The flangebearings 29 themselves are, however, not significantly distorted and arefree to swivel back and forth on the axle shaft 27 a. Therefore, theflange bearings 29 can easily and immediately be replaced on-site whenworn, eliminating much down-time that would be required ifconventionally designed axle casters were used in the conveyor cart 20of the present invention.

Adjacent carts 20 in the train are connected together using hitchmechanisms 32. Each hitch mechanism 32 is shown in FIGS. 3 and 4 asincluding a front hitch 32 a mounted on the front end of the base member24 in front of the roller structure 26 and a rear hitch 32 b mounted onthe rear end of the base member. In the embodiment disclosed, each hitch32 a,b has a vertical throughbore, through which a hitch pin connector32 c is inserted. Preferably, the hitch mechanisms 32 are configured sothat the front hitch 32 a on a rearward cart is disposed overtop of therear hitch 32 b on a forward cart. In the alternative, the hitchmechanisms 32 may comprise a poly-directional spherical ball jointmechanism similar in structure to an automotive trailer hitch. In eithercase, friction between hitch mechanism components is preferably reducedby, for example, lining the hitch components with TEFLON® or otherrelatively friction-free material.

To prevent adjacent conveyor carts 20 from separating should the hitchmechanism 32 accidentally break or become uncoupled, an auxiliary cartconnector 34 is preferably connected between the trailer framestructures 22 of adjacent carts 20. In the preferred embodiment, theauxiliary cart connector 34 is a metal cable or lanyard, although otherhigh-tensile strength materials could be used. In the embodimentdepicted, the auxiliary cart connector 34 is an approximately {fraction(3/16)}th inch thick metal cable connected to adjacent trailer framestructures 22 with metal mounting connectors 34 a.

The primary reason that metal is the preferred material for theauxiliary cart connector 34, besides its strength, is so that theauxiliary cart connector 34 will also serve as a continuous electricalconnector between adjacent carts 20. Electrical continuity between carts20 is important because of static electricity build-up while the carts20 are traveling around the conveyor track 12. However, because the camfollowers 30 a,b,c are preferably formed of polyurethane (an electricalinsulator) and because the components of the hitch mechanism 32 arepreferably coated with TEFLON® (also an electrical insulator),electrical continuity between adjacent carts 20 would not otherwise beeffectively achieved. By electrically connecting the carts 20, staticcharges can be bled off from the train, which is important for safetyand operational considerations. Thus, the auxiliary cart connector 34serves two important purposes: first, it physically attaches twoadjacent conveyor carts 20 and prevents them from becoming completelyseparated should the hitch mechanism 32 fail; second, it enableselectrical continuity among all of the conveyor carts 20 in the train.

The configuration of the conveyor cart 20 of the present invention, withits forwardly mounted roller structure 26, particularly structured hitchmechanism 32, and swept-back fin 36 is a significant improvement overpreviously designed conveyor carts. In conventional conveyor carts, theroller structures are typically mounted at the rear end of the trailerframe and the rear hitch is disposed overtop of the forward hitch. Whena hitch mechanism breaks or becomes accidentally uncoupled with this oldconfiguration, the result is that the forward end of the trailer framedrops below the conveyor track and is pushed over underlying structuresor the floor. As this uncoupled cart contacts the surrounding permanentstructures, the force exerted by the mass and acceleration of the cartsleads to inevitable damage to the sorter carts, the conveyor track, andthe surrounding structure. This occurrence is similar to a railroadtrain becoming derailed from the tracks causing massive damage to theindividual carts, the railroad track and any surrounding structure thatthe train contacts.

With the present design, even without the auxiliary connector cable 34,only the rear end of the trailer frame structure 22 will drop below theconveyor track 12 upon accidental disengagement of the hitches 32 a,b orupon breakage of the hitch mechanism 32. Therefore, instead of the frontend 36 a of the driven fin 36 digging into the floor, sides orunderlying structures below the conveyor, as is the case with prior artconveyors, the driven fin 36 will simply be dragged with relativelyminimal damage should one of the hitches 32 break or become accidentallyuncoupled. If an auxiliary connector cable 34 is attached between twoadjacent carts 20 that break apart, the connector cable 34 will limitthe distance that the rear end of the trailer frame structure 22 willdrop, further limiting damage.

Mounted atop the trailer frame structure 22 of each conveyor cart 20 isthe tiltable support apparatus 50, which supports the carrying tray 40thereabove. As can best be seen in FIG. 5, the tiltable supportapparatus 50 generally includes three components: an upper supportstructure 52 joined to a bottom surface of the carrying tray 40, a lowersupport structure 58 centrally mounted atop the longitudinal base member24, and an angled pivot structure 60 pivotally connecting the lowersupport structure 58 to the upper support structure 52 along a pivotaxis 62.

In turn, the upper support structure 52 includes a front support member54 and a back support member 56. The lower support structure 58 ispreferably generally planar, lying in the vertical plane parallel to theconveyor line of travel 64, and includes an angled upper edge 58 a. Thepivot structure 60 preferably includes an axle 68 that runs eitherthrough or along the upper edge 58 a of the lower support structure 58and is connected to the front and back support members, 56, 58,respectively. Preferably, the axle 68 runs through lower regions of thefront and back support members 56, 58. As can be seen, the front supportmember 54 depends farther down from the carrying tray 40 than the backsupport member 56. While the lower support structure 58 is stationarilyfixed to the trailer frame 22, the axle 68 allows the upper supportstructure 52 to pivot along the pivot axis 62 of the pivot structure 60.

In an alternate embodiment of the tiltable support apparatus (notshown), the upper support structure 52 could also comprise, like thelower support structure 58, a generally planar member that lies in thevertical plane parallel to the conveyor line of travel 64. In this case,the angled pivot structure 60 could take on the form of a hingestructure joining together the two generally planar support structures52, 58.

The pivot axis 62 lies in a vertical plane parallel to the conveyor lineof travel, which is shown in the drawings as horizontal line 64.However, unlike conventional sorter conveyor tilting carts, the pivotaxis 62 of the conveyor cart 20 of the invention is disposed at an angleθ to the conveyor line of travel 64 so as to impart two axial componentsto the tilting of the carrying tray 40. Preferably, the pivot axis 62 isangled downwardly at an angle of approximately 20 to 45 degrees belowhorizontal in a forward direction. In the embodiment disclosed, thepivot axis 62 is angled downwardly 30 degrees. As can be seen in FIG. 5,the pivot axis 62 preferably intersects a plane occupied by the carryingtray 40 rearward of the center of the tray 40.

By disposing the pivot axis 62 at a downwardly directed angle θ insteadof parallel to the conveyor line of travel 64, two axial components areimparted to the tilting motion of the carrying tray 40. The first axialcomponent of the tray's tilting motion is lateral tipping on ahorizontal axis parallel to the conveyor line of travel 64. The secondaxial component of the tray's tilting motion is rotating around avertical axis 66 perpendicular to the conveyor line of travel. Thus,while the tray only tilts along a single, angled pivot axis 62, theoverall motion of the tray 40 as it tilts includes two axial components.

The tilting motion of the tray may also be described usingthree-dimensional X, Y, and Z-axis spatial coordinates, as shown in FIG.5A, wherein the Y-axis is parallel to the conveyor line of travel 64,the X-axis extends horizontally perpendicular to the line of travel 64,and the Z-axis extends vertically perpendicular to the line of travel64. In the present invention, tilting of the tray 40 includes a Y-axisand a Z-axis component, for as shown in FIG. 5A the pivot axis 62intersects the Y and Z axes. Specifically and for illustrative purposesonly, using the preferred 37.5 degree downward angle θ of the pivot axis62, it can be appreciated that the ratio of Y-axis motion to Z-axismotion is 60:30. In other words, with a 30 degree angle θ, the tray 40laterally tips somewhat farther than it rotates. If the angle θ of thepivot axis 62 is increased to 45 degrees below horizontal, then the traywill tilt and rotate equally.

As shown in FIGS. 6 and 6A, one effect of this two-axis tilting of thecarrying tray 40 is that a side 44 b of the tray that is tilteddownwardly also rotates rearwardly relative to the cart 20, as shown inFIG. 6A by line 46 a. Side 44 d of the tray, which is tilted upwardly,rotates forwardly relative to the cart 20, as shown in FIG. 6A by line46 b. In the preferred embodiment, in which the pivot axis 62 intersectsthe plane occupied by the tray 40 rear-of-center, the front side 44 a ofthe tray 40 rotates a greater distance around the vertical axis 66 thanthe back side 44 c of the tray 40, upon tilting of the tray 40. As shownin FIG. 6A, the bisecting center line of the tray 40 rotates farther atits forward end from the horizontal line of travel 64 than at itsrearward end. Thus, front side rotation line 48 a follows a longer arcthan back side rotation line 48 b. By rearwardly rotating whichever sideof the tray 40 is being tilted downwardly, some rearward velocity isimparted to packages 11 as they are being discharged from the cart 20 ofthe invention into an unloading station 18. Thus, packages aredischarged at a lower velocity relative to the unloading station thanthe velocity of the train of conveyor carts as a whole. This enables thepackages to be discharged into a narrower chute than could beaccomplished using a conventional conveyor cart. Additionally, becausethe packages are slowed down somewhat as they are discharged, there isless potential for damage to occur.

As can be seen in the drawings, the tray 40 may also include upwardlyangled lateral wings 42 to help prevent packages 11 from accidentallyfalling off the tray 40. These wings 42 also decrease the angle of theslope created when the tray 40 is tilted, which helps with gentlehandling of the packages 11 as they are discharged from the cart 20.

When a carrying tray 40 reaches a particular destination unloadingstation 18, the tilting mechanism 80 tilts the carrying tray 40 to causea package 11 carried thereon to be discharged into the unloading station18. The tilting mechanism 80 generally includes components mounted oneach conveyor cart 20 and components associated with each unloadingstation 18. First is a pair of actuating arms 82 attached beneath eachcart's carrying tray 40 on opposite lateral sides thereof, one actuatingarm 82 on each side of the cart's tiltable support apparatus 50. Secondis a pull-down mechanism 90 immediately upstream from each unloadingstation 18. The pull-down mechanism 90, when activated, selectivelypulls down one of the actuating arms 82 and thereby pulls the respectiveside of the tray 40 downwardly and rearwardly into the biaxially tiltedposition described above. Third is a push-up mechanism 110 downstream ofthe unloading station 18, which pushes up the actuating arm 82 pulleddown by the pull-down mechanism 90 and thereby reorients the tray 40into its normal, upright position. Fourth is a locking structure 120,which locks the carrying tray 40 in the tilted position upon pullingdown of one of the actuating arms 82, and which also locks the carryingtray 40 in its normal, upright position upon pushing up of thatactuating arm 82.

Referring now to FIGS. 7 and 7A each actuating arm 82 is pivotallyattached to the underside of one side of the carrying tray and ispreferably connected to the front and back support members, 54 and 56respectively, of the upper support structure 52. In the embodimentshown, the actuating arm 82 is attached to the front and back supportmembers by an angled pivot hinge axle 84 that runs through both supportmembers 54, 56 and through the upper end of the actuating arm 82. Theactuating arm 82 therefore pivots on a pivot axis 86 that is preferablyparallel to the pivot axis 62 of the tiltable support apparatus 50, asshown in FIG. 5. As can be seen from an examination of the drawings, theactuating arms 82 and their respective pivot axes 86 remainsubstantially in a vertical plane parallel to the conveyor line oftravel 64 when stationary and when being pulled down or pushed up.

Each actuating arm 82 also includes a roller wheel 88, which engages thepull-down and push-up mechanisms 90, 110, as will bedescribed below. Theroller wheel 88 is preferably mounted on the lower end of the actuatingarm 82 on an outer surface 82 a thereof. It is conceivable, however,that the roller wheel 88 could be replaced with a friction reducingslide block or other protrusion for engagement by the pull-down andpush-up mechanisms 90, 110.

Under certain conditions, such as packages 11 of greater weight, theactuating arm 82 can develop stress fractures in the area of theconnection with the roller wheel 88 due to repeated engagement with thepull down mechanism 90. As can be seen in FIGS. 12 and 13, it ispreferable to connect the wheel 88 to the arm 82 with a cam bracket 230.The bracket 230 includes an axle portion 232 upon which the roller wheel88 is mounted. As can be seen in FIG. 13, the bracket 230 also includesan elongated portion 234 extending upwardly into the actuating arm 82.As can be seen in FIG. 12, the cam bracket 230 is preferably L-shaped.

Seen in detail in FIGS. 8, 8A, 9, and 9A, a pull-down mechanism 90 isassociated with each unloading station 18 and is located beneath therail 14 running closest to the unloading station 18 on the upstream sidethereof, as indicated in FIG. 6A. The pull-down mechanism 90 includes adescending ramp 92 and a laterally pivoting switch 94 that, whenactuated, pivots open and directs the roller wheel 88 of a passingactuating arm 82 into the descending ramp 92. As can be seen in thedrawings, when the switch 94 is not actuated, the switch is in a closedposition parallel to the ramp 92, and the roller wheel 88 is free tobypass the switch and the descending ramp 92. However, when a particularpackage 11 arrives at its destination unloading station 18, the switch94 is automatically actuated so that it pivots open into the path of thepassing roller wheel 88, capturing the roller wheel 88 throughengagement with a closure flange 104. The roller wheel 88 then isdeflected into alignment with, and into, the descending ramp 92. Thedescending ramp 92 forces the roller wheel 88 and the associatedactuating arm 82 downwardly so as to pull down one side of the tray 40,thereby discharging the package from the tray 40 into the unloadingstation 18 adjacent the pull-down mechanism 90.

On the upstream side of the laterally pivoting switch 94 is located asafety deflector 222. In a preferred embodiment, the deflector isgenerally wedge shaped, with an inwardly sloped ramp. The inwardlysloped ramp of the deflector 222 directs the roller 88 laterallyinwardly so that the roller 88 cannot not unintentionally contact eitherthe switch 94 if in a closed position or the descending ramp 92. Suchunintentional contact could cause damage to the laterally pivotingswitch 94, the descending ramp 92, the roller 88 or the actuating arm82.

The pull down mechanism 90 also includes a transverse guide 212 locatedopposite to, and coextensive with, the laterally pivoting switch 94. Thetransverse guide 212 controls the transverse position of the roller 88after contact with the switch 94. It has been found that the rolleroften rebounds inwardly after contact with the switch 94. Ifuncontrolled, the inward deflection has been found to cause the roller88 to contact the inside wall of the pull down mechanism, resulting inunacceptable levels of noise. The transverse guide 212, located oppositethe switch 94, creates a channel to direct the transverse movement ofthe roller 88. The transverse guide 212 is preferably an outwardlysloped ramp. The ramp preferably has a first transition zone 214 locatedat the upstream side of the guide 212. The roller 88 is thereby guidedinto contact with the switch 94 by a feeder area created by the closureflange 104 and the first transition zone 214. The roller 88 passed fromthe first transition zone 214 leads into a parallel zone 216. Theparallel zone 216 is parallel to the open position of the closure flange104. A second transition zone 220 then leads the roller 88 from theparallel zone 216 into alignment with the descending ramp 92. The safetydeflector 222 is located upstream of the transverse guide 212,preferably adjacent thereto.

A computer controller (not shown) is used to track all packages 11moving on the conveyor 10 and to automatically actuate a switch 94 atthe appropriate time when a particular package 11 reaches itsdestination unloading station or outfeed chute 18. The computer is alsoconnected to the LIM 70 to control the movement of the conveyor trainand maintain a desirable rate of speed.

In a preferred embodiment, the pivot switch 94 is attached to abi-directional actuator 150 as shown in FIGS. 8 and 8A. Thebi-directional actuator is mounted below the pivot switch 94 away fromthe moving roller wheels. As shown in FIG. 11, the bi-directionalactuator 150 includes a coaxial arm 152 extending from an actuator motor154 and connected to the interior of the pivot switch 94.

The actuator motor 154 rotates the coaxial arm 152 and the attachedpivot switch 94 between the open position to capture the roller wheel 88and the closed position to allow the roller wheel to bypass theunloading station. Power and communication means with the conveyorsystem is supplied to the actuator motor 154 via a cord 160. To rotatethe coaxial arm to an open position, power is continuously applied tothe motor to maintain the pivot switch in the open position. When poweris turned off, a coil spring positioned inside the actuator motor 154biases the arm causing the pivot switch to rotate to the closedposition. This combination of powered on and powered off enables thepivot switch to be controlled independently of the movement of theroller wheels. In one embodiment, the actuator motor is a 500 Model40R10102-10-11 rotary solenoid actuators (“the model 40R actuators”)from Ram Manufacturing Company, Inc. The actuator motor 154 is mountedwithin a heat sink 172.

As best seen in FIG. 11, an outer clevis 162 surrounds the actuator arm152 and is mounted between an upper bracket 164 and a lower bracket 166.The outer clevis 162 is mounted to a lower body 174 that is alignedsubstantially perpendicular to align with the lower bracket 166.Connector means such as screw or bolts mount extend through the lowerbracket 166 and lower body 174 to secure the bidirectional actuator tothe tipping mechanism. The outer clevis 162 is sized larger than theactuator arm 152 such that as the arm rotates, the clevis maintains afixed position. A roll pin 170 extends through the actuator arm 152 andouter clevis 162 and into the interior of the pivot switch 94. The rollpin 170 is fixedly attached to the actuator arm 152 such that therotation of the actuator arm moves the pin which thereby moves the pivotswitch through the open and closed positions. The roll pin extendsthrough apertures within the outer clevis such that the pin has a freerange of movement.

The outer clevis 162 and upper bracket 164 and lower bracket 166 protectthe actuator arm 152 from stresses applied to the pivot switch 94. Theouter clevis 162 allows for the pivot switch to pivot about the clevis,but prevents the pivot switch from moving in a linear direction whichcould damage the actuator arm.

In use, the actuator motor 154 is energized thereby rotating theactuator arm 152 causing the pivot switch to rotate to the openposition. The next passing cam follower will be captured by the pivotswitch and diverted into the unloading station path. After the camfollower has been captured, power to the actuator motor 152 will bestopped causing the inner coil spring to bias the pivot switch in theclosed position. However, while the cam follower is running along thelength of the pivot switch, the force of the wheel will maintain theswitch in the open position. Once the cam follower has passed downstreamof the pivot point, the pivot switch will rotate to a closed position bythe biasing of the internal coil spring.

This arrangement provides for the pivot switch to be maintained in anopen position for the shortest duration thereby allowing the speed ofthe sorter conveyor to be increased over previous designs without theproblem of the switch inadvertently remaining open and catching the nextpassing cam follower thereby starting the cascade effect. Powering downthe pivot switch to the closed position will also remove inadvertentcaptures such as when a cam follower is missing from the actuating armor if the cam follower were to jump the pivot switch without enteringthe unloading station. Previously available designs depended upon thecam followers passing along the pivot switch to rotate the pivot switchto the closed position.

After the carrying tray 40 has been tilted and a package carried thereonhas been discharged into an unloading station 18, the carrying tray isreoriented into its normal upright position by the push-up mechanism110. Seen best in FIGS. 10 and 10A, a push-up mechanism 110 isassociated with each unloading station 18 and is located beneath thetrack 12 adjacent the unloading station 18 on the downstream sidethereof, as indicated in FIG. 6A. Each push-up mechanism 110 includes anascending ramp 112 below the rail 14 adjacent the unloading station 18.The push-up mechanism 110 also includes a wedge-shaped frog 114 thatengages the cam follower 88 on a pulled-down actuating arm 82 anddirects the cam follower 88 into the ascending ramp 112. The frog 114 ispositioned low enough below the track 12 so that cam followers 88 willbe engaged and directed into the ascending ramp 112 only if they havealready been pulled down by the pull-down mechanism 90. As the camfollower 88 is directed into the ascending ramp 112, the actuating arm82 is pivoted outwardly somewhat so that the outside edge 123 of thelocking flange 122 will disengage from the tilted position lockingchannel 127. To help pull the actuating arm 82 back into substantiallyvertical alignment after the locking flange 122 has slid over the slidesurface 130, the top of the ascending ramp 112 includes an inwardlyturned section 116.

Now turning to the locking structure 120 of the tilting mechanism 80, itcan be seen best in FIGS. 7 and 7A that the locking structure 120includes a pair of locking flanges 122, a pair of locking blocks 124mounted one each to the actuating arms 82, and a biasing member 134 forbiasing the actuating arms 82 inwardly into a locked position.Preferably, the locking flanges 122 laterally extend from both sides ofthe lower support structure 58 of the tiltable support apparatus 50,although they could also be mounted to the trailer frame structure 22.In the embodiment disclosed, the locking flanges 122 comprise generallyplanar steel plates having rollers 123 mounted to their outer edges 123.In an alternate embodiment, the rollers 123 could be eliminated and thelocking blocks 124 made of a low-friction material on which theroller-less outer edges of the locking flanges 122 could easily slide.

Each locking block 124 is mounted to an inner surface 82 a of theactuating arm 82 and includes two locking channels 126 and 134 separatedby a cammed section 130 having a generally convex outer surface. Thelower 126 of the two locking channels receives the roller 123 at theouter edge of the lateral locking flange 122 when the carrying tray 40is in its upright position. The upper 134 of the two locking channelsreceives the roller 123 when the carrying tray 40 is in its tiltedposition. As the tray 40 is tilted from one position to the other, theroller 123 rolls over the cammed section 130 interposed between the twolocking channels 126, 134. Preferably, the locking blocks 124 are madeof a wear-resistant material such as plastic, although other materialscould be used. The biasing member, which may be a spring 134, pulls theactuating arms 82 inwardly so as to engage the locking structure 120 byseating the locking flanges 122 in one of the locking channels 126, 134.

During tilting of the tray 40 by the pull-down mechanism 90, theactuating arm 82 being pulled down is pivoted outward slightly on thepivot axis 86 as the cam follower 88 is captured by the switch 94 anddirected into the descending ramp 92. This outward pivoting of theactuating arm 82 causes the upright position locking channel 126 todisengage from the locking flange 122. Then, as the cam follower 88 ispulled down by the descending ramp 92, the locking flange 122 rollsupwardly over the cammed section 130. Because of the curved, convexshape of the cammed section 130 of the locking block 124, the actuatingarm 82 remains substantially vertical as it is pulled down. This helpsprevent the cam follower 88 from slipping out of the descending ramp 92of the pull-down mechanism 90. Eventually, the locking flange 122 isseated in the tilted position locking channel 134 as the wheel exits thedescending ramp 92 and the tray 40 reaches its fully tilted position.The degree to which the tray 40 is tilted in the fully tilted positioncan vary depending on the configuration of the locking blocks 124 andthe pull-down mechanism 90. However, in the embodiment disclosed, thetray 40 is tilted approximately 37.5 degrees from horizontal in thefully tilted position.

The biasing member 134 holds the tilted position locking channel 134 andthe locking flange 122 together while the cart 20 is moving past theunloading station 18, stabilizing the tray 40 in the tilted position.Then, when the downwardly pulled actuating arm 82 reaches the push-upmechanism, the arm 82 is pivoted outwardly by the wedge-shaped frog 114engaging the cam follower 88. This outward pivoting causes the lockingflange 122 to disengage from the tilted position locking channel 134. Asthe cam follower 88 moves up the ascending ramp 112, the locking flangerolls downwardly over the cammed section 130. As the inwardly turned topend 116 of the ascending ramp 112 pivots the actuating arm 82 back toits vertical orientation, the locking flange 122 seats in the uprightposition locking channel 126, where it is held in place through theaction of the biasing member 134.

The actuating arm 82 on the opposite side of the conveyor cart 20, whichis not being pulled down or pushed up at a particular unloading station18, simply rises and falls with the side of the tray 40 to which it isattached. The locking flange 122 on this side of the cart 20 simplyrolls over a flat section 132 of the locking block 124 below the uprightposition locking channel 126.

In an alternate embodiment (not shown) of the package sorting conveyor10 of the invention, the conveyor cart 20 could include a tiltablesupport apparatus having a pivot axis that is not angled downwardly butthat is generally parallel to the conveyor line of travel 64. In thiscase, the tilting motion of the carrying tray 40 would only have asingle axial component—lateral tipping on a horizontal axis parallel tothe conveyor line of travel 64. While package sorting conveyors having asingle-axis lateral tipping motion have been designed in the past, theydo not include the other inventive features of the present sortingconveyor 10 such as the vertically oriented LIM 70, the hitch mechanism32 and auxiliary cart connector 34, and the tilting mechanism 80 withits associated components.

Such single-axis conveyor carts would primarily be incorporated into thepackage sorting conveyor 10 of the present invention for use in sortingparticularly large packages that must be carried by two or more adjacentcarrying carts 20. In this case, the trays of the adjacent carts wouldbe simultaneously tilted as the carts reached an unloading station todischarge the package. This would also of course require an especiallywide outfeed chute as well as a pull-down mechanism adjacent theunloading station for each cart to be simultaneously tilted.

The reason that single-axis conveyor carts are especially useful forsorting large packages is that it has been found that this double (ortriple, etc.) unloading of particularly large packages using thetwo-axis carrying carts 20 of the present invention occasionallypresents difficulties due to the carrying trays 40 not being in the samespatial plane when they are both in their fully tilted positions.Therefore, for double unloading, it is preferable to use the alternate,single-axis embodiment of the conveyor cart.

Several configurations of the package sorting conveyor 10 may beemployed that utilize the alternate, single-axis conveyor carts fordouble unloading situations. A preferable configuration would comprisetwo adjacent single-axis carts for carrying a single large package. Asecond configuration would comprise a leading two-axis conveyor cart 20and a trailing single-axis cart. A third configuration would comprise aleading single-axis conveyor cart and a trailing two-axis conveyor cart20. As a whole, the package sorting conveyor 10 of the invention mayinclude both two-axis conveyor carts 20 as well as single-axis conveyorcarts interspersed among each other depending on a particular facility'sconveying and sorting requirements.

The benefit of the present invention can best be understood, from thefollowing sound tests comparing the present invention to the prior arttipper.

TABLE 1 TRANSVERSE GUIDE SOUND TESTING (DBS) Speed Ambient (FPM) WithGuide Without Guide sound 100 63 65 60 150 67 67 61 200 69 69 63 250 7172 64 300 78 80 70 350 80 83 71 400 81.5 88 72 415 82.5 88 80

Measurements taken with Radio Shack, Realistic Sound Meter model/cat no.33-2050 from a distance of 30.25 inches.. Weighting set on “A”, Responseset to “Fast”

As can, even at very high speeds the present invention is about one-halfthe decibel increase as the increase caused by tipping without thetransverse guide of the present invention.

Since dB is a logarithmic scale, each 10 dB change corresponds to adoubling of sound pressure but a 5 dB change is only the threshold atwhich a human can detect a difference in loudness. Accordingly, at amaximum tested speed of 415 fpm, a sorter being tipped, without thepresent invention, is almost twice as loud (88 v. 80) as a sorter whichis not being tipped at all but is running at the same speed. To thecontrary, at a maximum tested speed of 415 fpm, a sorter being tipped,with the present invention, is almost undetectable to a human ear (82.5v. 80) as a sorter which is not being tipped at all but is running atthe same speed. Thus, like a rifle suppressor, the report of the tipperis substantially reduced.

Certain modifications and improvements will occur to those skilled inthe art upon a reading of the foregoing description. It should beunderstood that all such modifications and improvements have beendeleted herein for the sake of conciseness and readability but areproperly within the scope of the following claims.

We claim:
 1. A sorting conveyor for transporting objects and unloadingobjects at one or more unloading stations adjacent the conveyor, saidsorting conveyor comprising: (a) a conveyor track; (b) a train oftilting conveyor carts connected end-to-end; (c) a power source formoving said conveyor carts on said conveyor track; (d) each of saidtilting conveyor carts comprising: (i) a trailer frame base, including:a roller structure for engaging said conveyor track, a driven memberresponsive to said power source, and a hitch mechanism for connectingeach tilting conveyor cart to an adjacent conveyor cart; (ii) a carryingtray for holding the objects; and (iii) a tiltable support apparatus forsupporting said carrying tray above said trailer frame base and forallowing tilting of said carrying tray towards at least one side of theconveyor to unload objects into unloading stations on at least one sideof the conveyor; and (e) a tilting mechanism for tilting said carryingtray on said tiltable support apparatus to thereby unload objects intoone of the unloading stations adjacent the conveyor, wherein saidtilting mechanism includes: (i) a pair of actuating arms attached tosaid carrying tray on opposite sides of said tiltable support apparatus;and (ii) a pull-down mechanism associated with each unloading stationfor selectively pulling down one of said actuating arms so as to pullone side of said carrying tray downwardly into a tilted position;wherein each of said actuator arms includes a cam follower on a lowerend of said actuator arm, and wherein said pull-down mechanism includesa descending ramp adjacent said conveyor track, a laterally pivotingswitch for directing the cam follower of a selected actuator arm intosaid descending ramp and a transverse guide for controlling the positionof said actuator arm to reduce noise during tipping.
 2. The apparatusaccording to claim 1, wherein said sorting conveyor includes at leastone single-axis conveyor cart that comprises a tiltable supportapparatus having a horizontal pivot axis that is disposed generallyparallel to the conveyor line of travel.
 3. The apparatus according toclaim 1, wherein said hitch mechanism comprises a front hitch on a frontend of said trailer frame base, a rear hitch on a rear end of saidtrailer frame base, and a hitch connector for connecting the front hitchof one conveyor cart to the rear hitch of an adjacent conveyor cart. 4.The apparatus according to claim 3, wherein the front hitch is disposedovertop of the rear hitch.
 5. The apparatus according to claim 1,wherein said trailer frame base comprises an auxiliary cart connectorfor connecting each tilting conveyor cart to an adjacent conveyor cartto prevent adjacent conveyor carts from separating upon failure of saidhitch mechanism.
 6. The apparatus according to claim 5, wherein saidauxiliary cart connector comprises an electrically conductive cableconnected at one end to said trailer frame base and at another end to atrailer frame base of an adjacent conveyor cart.
 7. The apparatusaccording to claim 1, wherein said power source comprises a linearinduction motor, and wherein the driven member of said trailer framebase comprises a metal fin moved in the conveyor line of travel by saidlinear induction motor.
 8. The apparatus according to claim 7, whereinsaid linear induction motor comprises two opposing out-of-phaseelectromagnets.
 9. The apparatus according to claim 7, wherein saidlinear induction motor and said metal fin are both vertically orientedbeneath said trailer frame base.
 10. The apparatus according to claim 9,wherein said metal fin is generally parallelogram-shaped with rearwardlyangled front and rear edges.
 11. The apparatus according to claim 1,wherein said tilting mechanism further includes a locking structure forlocking said carrying tray in the tilted position upon pulling down ofone of said actuating arms, and for locking said carrying tray in theupright position upon pushing up of said actuating arm and said tiltablesupport apparatus further includes: (i) an upper support structurejoined to said carrying tray, (ii) a lower support structure joined tosaid trailer frame base, and (iii) a pivot structure connecting theupper support structure to the lower support structure along a pivotaxis.
 12. The apparatus according to claim 11, wherein said actuatingarms are pivotally attached to said carrying tray beneath said carryingtray.
 13. The apparatus according to claim 12, wherein the pivot axes ofsaid actuating arms are parallel to the pivot axis of said tiltablesupport apparatus.
 14. The apparatus according to claim 12, wherein saidactuating arms are pivotally attached to said upper support structure ofsaid tiltable support apparatus.
 15. The apparatus according to claim12, wherein the pivot axis of said pivot structure lies in a verticalplane parallel to the conveyor line of travel, and wherein saidactuating arms remain substantially parallel to the vertical planeparallel to the conveyor line of travel during pulling down and pushingup of said actuating arms to tilt said carrier tray.
 16. The apparatusaccording to claim 11, wherein said locking structure includes: (a) apair of laterally extending locking flanges on opposite sides of saidtiltable support apparatus; (b) a pair of locking blocks mounted toinner surfaces of said actuating arms, each locking block having lockingchannels that receive said locking flanges; and (c) a biasing memberattached to both actuating arms for biasing said actuating arms towardseach other so as to urge said each of said locking flanges into one ofsaid locking channels.
 17. The apparatus according to claim 16, whereineach locking block includes a locking channel associated with the tiltedposition of said carrying tray, and wherein each locking block includesa locking channel associated with the upright position of said carryingtray.
 18. The apparatus according to claim 17, wherein each said lockingflange includes a roller mounted to an outer edge thereof.
 19. Theapparatus according to claim 18, wherein each said locking blockincludes a cammed section between said locking channels over which saidrollers on the outer edges of said locking flanges roll.
 20. Theapparatus according to claim 1, wherein said conveyor track comprisestwo parallel rails.
 21. The apparatus according to claims 20, whereineach said cam follower mechanism includes an axle caster that holds acam follower, each said axle caster including two forks, a bearing boredisposed at a juncture between said two forks, and at least one flangebearing seated within said bearing bore and disposed around an axleshaft extending from said roller structure.
 22. The apparatus accordingto claim 21, wherein said cam follower is held in place in said axlecaster by a nut and bolt extending through said cam follower and both ofsaid forks, wherein said axle caster also includes an opening on oneside of said bearing bore that communicates with a space between saidtwo forks, and wherein said at least one flange bearing is securedwithin said bearing bore by tightening said nut and bolt so as toinwardly flex said two forks towards each other, thereby slightlyclosing said opening and distorting said bearing bore.
 23. The apparatusaccording to claim 20, wherein said trailer frame base includes alongitudinal base member that extends between the two parallel railsparallel to the conveyor line of travel.
 24. The apparatus according toclaim 23, wherein said roller structure comprises two laterallyextending cam follower mechanisms, one cam follower mechanism riding oneach conveyor track rail.
 25. The apparatus according to claim 24,wherein the cam follower mechanisms are attached to a forward end ofsaid longitudinal base member.
 26. The apparatus according to claim 24,wherein each conveyor track rail is supported only on an outside edge,and wherein each cam follower mechanism comprises three cam followers.27. The apparatus according to claim 26, wherein each cam followermechanism includes an upper cam follower for riding on a top edge of atrack rail, a middle cam follower for riding on an inside edge of thetrack rail, and a lower wheel for riding on a bottom edge of the trackrail.